In recent years, there have been increasing vehicle thefts and thus various antitheft apparatus have been used in vehicles. As one of such antitheft apparatus, there is known a lock apparatus which disables the operation of a steering wheel unless a regular key is used. The lock apparatus, as shown in, for example, the patent reference 1 to 4, includes a lock unit provided on a steering column and a key lock groove formed in a steering shaft. And, in operation (in key locked operation), a lock pin provided on the lock unit is inserted into the key lock groove to thereby prevent the rotation of the steering shaft.
In order to secure a sufficient antitheft effect which is provided by such lock apparatus, in a state where the function of the steering apparatus remains secured, it is necessary that the lock unit cannot be removed. In the patent reference 1, there is disclosed a lock apparatus which is structured to be able to meet such need.
In the steering apparatus including the lock apparatus disclosed in the patent reference 1, a lock housing for storing the lock apparatus therein is constituted of a part formed separately from an outer column, and the lock housing is mounted on the outer column for rotatably supporting a steering shaft using a bolt. When such separate lock housing is mounted onto the outer column using a bolt in this manner, it is difficult to enhance the rigidity of the lock housing which receives a reaction force given when the steering shaft is locked. Thus, there is raised a problem that the number of parts and the weight of the lock housing must be increased in order to compensate the shortage of the rigidity of the lock housing.
Also, as disclosed in the patent reference 5, there is proposed a steering apparatus including a clamp device for adjusting the telescopic position of a steering shaft and a lock apparatus for locking the steering shaft. However, in this steering apparatus, there is also raised the following problem.
That is, in the clamp device, the telescopic position of the steering shaft can be adjusted using a slit which is formed in an outer column. In other words, the clamp device applies a fastening force to the outer column to reduce the width of the slit to thereby prevent the steering shaft and outer column from moving relative to each other, while, when the fastening force of the clamp device is relieved, the width of the slit is increased to thereby allow the telescopic movement of the steering shaft relative to the outer column, whereby the clamp device is allowed to adjust the telescopic position of the steering shaft.
On the other hand, the lock apparatus includes a key lock groove formed in the steering shaft, a through hole formed in the outer periphery of the outer column, and a lock unit having a lock pin and disposed on the outer periphery of the outer column. When locking the steering shaft, the lock pin is inserted through the through hole of the outer column into the key lock groove of the steering shaft to thereby prevent the rotation of the steering shaft.
In the steering apparatus including the clamp device and lock apparatus structured in this manner, the slit of the clamp device and the through hole of the lock apparatus are formed in the same outer column. This reduces the strength of the portion of the outer column that exists near the slit and through hole. Thus, when the clamp device applies the fastening force to the outer column, there is a fear that there can be produced a crack between the slit and through hole.
This makes it impossible to dispose the slit and through hole adjacently to each other and, therefore, the mounting position of the lock apparatus is limited and the fastening force of the clamp device cannot be increased.    Patent Reference 1: Japanese Patent Publication 2006-36106    Patent Reference 2: Japanese Patent Publication 2004-237973    Patent Reference 3: Japanese Patent Publication 2004-98788    Patent Reference 4: Japanese Patent Publication 2006-36107    Patent Reference 5: Japanese Patent Publication 2000-168501